Musnad Ahmad 32:1367

Sayyar ibn Hatim narrated to us, Ja'far ibn Sulayman al-Duba'i narrated to us, Thabit narrated to us, from Anas, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Indeed, the birds of Paradise are like the Bactrian camels, grazing among the trees of Paradise." Abu Bakr said: "O Messenger of Allah, these are indeed soft/delicate birds." He said: "Those who eat them are softer/more delicate than them," he said it three times, "and I hope that you will be among those who eat from them, O Abu Bakr."